I've actually considered this and realized that a user rating of 4 is about ideal. Why? Because most people either vote 1 or 10 and nothing in-between. Now if you're really posting your mind and are somewhat intelligent, it's likely that you will piss off half the people who read your posts while the other half will like them. Those who you piss off will generally have no qualms against voting 1 right on the spot. OTOH, those who really liked your post will either forget to vote at all or will likely hold off on voting 10 on the off-chance that you might piss them off in the future and they won't be able to change their vote. Hence, a user rating of 4 means that you are probably pleasing more people than you are upsetting, with a good number thinking highly enough about your posts to actually stop and give you a 10 while still making sure to upset the appropriate (and needed) amount.
btw, I just turned off my user rating for this post, but it was at 3.84 with 64 voted. I might turn it back on in a few weeks.